Coating composition, granules coated with same, and method of reducing dust generation

ABSTRACT

A coatable composition suitable for reducing dust generation during processing of granular materials consists essentially of a tackifier, an organic oil, and an adhesion agent, the tackifier consisting essentially of an organic material having a glass transition temperature of no less than about 120° C. and a diluent present in sufficient amount to give the tackifier a kinematic viscosity ranging from about 3,000 to about 5,000 centistokes at 100° C. The tackifier is preferably present in the composition at about 0.5 to about 2.0 weight percent of the total weight of the composition, and the adhesion agent is preferably present at about 0.5 to about 5.0 weight percent of the total weight of the composition, with the balance being organic oil. Granular materials having coatings of the composition (with or without the adhesion agent) are presented, as well as methods of reducing dust generation during processing and/or transport of granular materials and methods of making organic oil-coated granular materials.

This is a division of application Ser. No. 08/026,441 filed Mar. 4, 1993now U.S. Pat. No. 5,362,566.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions consisting essentially ofan organic oil and a tackifier (which itself includes a diluent), thecompositions having an increased propensity to reduce dust generationfrom granular materials during processing of such materials comparedwith organic oils used alone.

2. Description of Related Art

Roofing granules, both natural and artificially color-coated, findextremely wide use in roofing and siding materials. Importantapplications are in granular surfaced bituminous roll roofing andasphalt shingles. The granules, which are partially embedded in onesurface of asphalt-impregnated and/or asphalt-coated fiber sheetmaterial, form a coating to provide an inherently weather-resistant,fire-resistant, and decorative exterior surface. "Weather-resistant" asused herein includes ultraviolet (UV) radiation-resistant.

Roofing granules generally consist of crushed and screened inorganicsubstrate granules. The substrate granules are typically coated with aceramic coating which may include a pigment. In carrying out thesecoating methods, the pigment is uniformly applied to the substrategranule surface with a soluble silicate solution. The coating is usuallyapplied in the form of a dispersion of a soluble silicate and a claywhich partially or completely react together in the presence of heat toform an insolubilized ceramic coating.

Dust generation during processing and handling of inorganic granulessuch as roofing granules presents an environmental (air quality) issuethat must be dealt with by the manufacturer and the customer, mostnotably at transfer points when unloading granules from shippingcontainers, such as trucks and railhoppers and the like, to storagetanks. Airborne particles of substrate and coating (particles range insize from 0.5 to about 30 micrometers) are typically generated duringprocessing and handling.

Various approaches have been taken to reduce dust generation, all havingcertain disadvantages:

a) dust generated from white roofing granules may be reduced by reducingthe amount of borax in the ceramic coating; however, this increasestitanium dioxide pigment costs;

b) another alternative to reduce dust generation is to use an organicoil, such as slate oil, coated onto the granules as a post-treatmentcoating. Increased oil usage however may decrease adhesion of roofinggranules to bituminous shingles. Oil can also increase color differencebetween color of the originally oiled granular material and color aftera given period of time. This is an especially important consideration inthe manufacture of roofing granules.

c) silicone oils and other adhesion agents added to the organic oil mayimprove adhesion of granules to asphalt-based shingles, as taught inassignee's U.S. Pat. Nos. 5,240,760 and 5,286,544; however, the problemsassociated with use of oil alluded to above remain;

d) magnesium chloride, applied in appropriate amounts, is touted ashaving the ability to reduce dust generation from inorganic granulesduring processing of the granules, as disclosed in assignee's U.S. Pat.No. 5,368,936; however, the alkalinity of magnesium chloride-treatedgranules must be closely scrutinized.

Given the above, it would be advantageous and an advancement in the artif the level of dust generated during processing and handling ofgranular materials such as roofing granules could be controlled whileavoiding the disadvantages of prior approaches to the problem.

SUMMARY OF THE INVENTION

In accordance with the present invention, a coatable composition ispresented which has as one primary utility the ability to reduce oreliminate dust generation during processing granular materials while atthe same time reducing the amount of oil required. As used herein theterm "coatable" means that the composition viscosity is such as to allowthe composition to be sprayed or poured onto granular materials.

The coatable compositions of the invention consist essentially of:

a) an organic oil;

b) an adhesion agent (such as a silicone oil); and

c) a tackifier, the tackifier consisting essentially of an organicmaterial having a glass transition temperature of no less than about120° C. (more preferably no less than about 150° C.) and a diluentpresent in sufficient amount to give the tackifier a kinematic viscosityranging from about 3,000 to about 5,000 centistokes at 100° C.

As used herein "kinematic viscosity" has its generally accepted meaning,the absolute viscosity (sometimes referred to as the dynamic viscosity)of the fluid divided by its mass density. Preferred diluents arelight-colored naphthenic oils.

The amount of tackifier in the inventive compositions preferably rangesfrom about 0.5 to about 2.0 weight percent, more preferably from about0.5 to about 1.0 weight percent of the total weight of the composition.The amount of adhesion agent preferably ranges from about 0.5 to about5.0 weight percent of the composition weight, the balance of thecomposition being organic oil.

The term "consisting essentially of", when used in reference to theinventive compositions, means that the compositions of the invention mayinclude impurities and additives which do not detract from the abilityof the compositions to reduce dust generation. When the term is used inreference to the tackifier component (typically a pre-formulatedadditive), the term means that the tackifier may include impurities andadditives which do not detract from the ability of the tackifier toincrease the viscosity of the organic oil.

Preferably, the organic oil is a mineral oil (i.e., a hydrocarbon oilderived from petroleum, such as paraffin oils, naphthenic oils, and thelike, or a coal oil or rock oil). One particularly preferred mineral oilis slate oil. Another particularly preferred mineral oil is seneca oil.These oils will generally have a kinematic viscosity ranging from about100 to about 300 centistokes at 100° C., more preferably ranging fromabout 150 to about 250 centistokes.

The organic material component of the tackifier is preferably selectedfrom organic monomers, oligomers or polymers having a glass transitiontemperature (T_(g)) no less than about 120° C., more preferably no lessthan about 150° C. Two categories of preferred organic polymericmaterials are polyalkylene resins and polycycloalkene resins, the lattergroup including aromatic organic resins.

Preferred organic materials which are polyalkylene resins includepolybutene resins, dipentene resins, terpolymers of ethene, 1-propene,and 1,4-hexadiene, and the like.

Preferred organic materials which are polycycloalkene resins includephenol-aldehyde resins; polyterpene resins; rosins, including rosinacids and esters, and hydrogenated rosins; polyethylene rosin esters;phenolic polyterpene resins; limonene resins; pinene resins such asalpha and beta pinene resins; styrenated terpene resins, and the like.

One particularly preferred tackifier consists of the terpolymer ofethene, 1-propene, and 1,4-hexadiene adjusted to the above preferredkinematic viscosity with a light-colored naphthenic oil, such as thenaphthenic oil known under the trade designation "HS-500", availablefrom Cross Oil & Refining Co., Smackover, Ark.

The present invention also provides a coated granular material which hasa dust-reducing coating (20-100 micrometers thick) of the composition ofthe invention applied as a post-treatment, either with or without theadhesion agent component of the composition. An adhesion agent ispreferably used if the granular materials are adhered to an extendedsurface, such as in a roofing shingle construction. In situations wherethe coated granular material is used without being attached to asurface, such as when the coated granular material is merely used as adecorative material in a garden or flower bed, it is preferred that anadhesion agent not be used.

The coated granular materials of the invention (with or without adhesionagent) preferably have present thereon the composition of the inventionin quantities sufficient to give the coated granular material a dustgeneration value of not more than 500 particles per cubic centimeter,more preferably not more than 100 particles per cubic centimeter. A testwhich defines "dust generation value" is given in the Test Methodssection. The amount of coating used in the inventive coated granularmaterials typically and preferably ranges from about 0.5 to about 10grams per kilogram of base granules, more preferably about 2.5 to about4 grams per kilogram of base granules.

Another aspect of the invention is a method of making organic oil-coatedcoated granular materials comprising the steps of:

a) providing a base granule; and

b) coating the base granule with the composition of the invention,preferably to a coating weight ranging from about 0.5 to about 10 grams,more preferably about 2.5 grams to about 4.0 grams of composition perkilogram of base granules.

A method wherein the composition is devoid of adhesion agent is alsodeemed within the invention. One advantage of the method of making theorganic oil-coated granular materials of the invention is that whenusing the above-described inventive compositions, the compositions donot gel (increase in kinematic viscosity over 500 centistokes measuredat 100° C.) in the containers in which the composition is held, asopposed to presently known post-treatment compositions.

Another aspect of the invention is a method of reducing dust generationduring processing of base granules, the method comprising treatinggranular materials with the composition of the invention. Preferably, aspreviously stated, the amount of the composition applied to the basegranules is at least about 0.5 grams per kilogram base granules, but nomore than about 10 grams per kilogram base granules.

Regarding this latter aspect of the invention, it has been discoveredthat the location in the process where the composition is applied to thebase granules is important to optimize the reduction in dust generationfrom base granules. In particular, in processes wherein silicate/claysolution-coated base granules are fired in a kiln (for example, acommonly known rotating kiln) to crystallize the coating to form a hardceramic coating, the kiln-fired granules are typically transferred to acooling means, such as a rotating water cooler, and then transportedutilizing one or more transport means (for example horizontal andvertical conveyer belts) downstream of the cooling means to a finalstorage facility, such as a railhopper car or holding tank. It has beenfound that if equal amounts of composition of the invention are appliedto the base granules materials while the base granules are being cooledin the cooling means to a temperature of about 110° C., and downstreamat the transport means where the temperature of the granules has reacheda temperature of about 80° C., as the percentage of tackifier in thecomposition increases the amount of dust generated significantlydecreases. Surprisingly, however, if all of the composition is appliedto the granules at the cooling means, there is no significant decreasein dust generation as the percentage of tackifier is increased fromabout 0.2 percent to about 1.0 percent, unless the quantity of thecomposition applied exceeds about 3 grams per kilogram of granules.

Preferred coated granular materials of the invention include inorganicbase granules having a ceramic coating, the ceramic coating consistingessentially of the reaction product of an alkali metal silicate and analuminosilicate (clay). Reduction in both the dust generated from baseinorganic granules and the amount of organic oil used are significant,as seen in the Examples.

Further understanding of the advantages of the invention will berecognized by reading the Description of Preferred Embodiments andExamples which follow.

DESCRIPTION OF PREFERRED EMBODIMENTS Tackifiers

As previously stated, "tackifiers" within the invention comprise anorganic material combined with (preferably dispersed in) a diluent. Itis preferred that the organic material comprise a thermally-stable,shear-stable polyolefin. The "tackiness" of the composition of theinvention may be decreased by shear, thus mechanical shearing duringblending and handling of the tackifier component and compositions of theinvention should be avoided or minimized.

Organic materials particularly well suited for use in the tackifier havealready been mentioned and include polybutene resins, dipentene resins,the terpolymer of ethene, 1-propene, and 1,4-hexadiene, and the like.Particularly preferred is the terpolymer of ethene, 1-propene, and1,4-hexadiene.

A non-limiting list of other commercially available organic resinshaving glass transition temperature no less than about 120° C. which maybe used as the organic material in tackifiers are those given in Table1, wherein T_(g) denotes the glass transition temperature, and T_(s)denotes the softening temperature of the resin. The trade designation,type of resin, and resin manufacturer or supplier is also given in Table1.

                  TABLE 1                                                         ______________________________________                                        ORGANIC RESINS USEFUL IN TACKIFIERS                                           Resin       Tg     Ts                                                         Trade Designation                                                                         °C.                                                                           °C.                                                                           Resin Type                                                                              Mfr                                       ______________________________________                                        Arkon P70   145    173    Hydrogenated                                                                            Arakawa                                                             C9                                                  Arkon P90   154    181    Hydrogenated                                                                            Arakawa                                                             C9                                                  Arkon P115  166    203    Hydrogenated                                                                            Arakawa                                                             C9                                                  Arkon P125  171    208    Hydrogenated                                                                            Arakawa                                                             C9                                                  Escorez 1102                                                                              154    189    C5 Resin  Exxon                                     Escorez 1304                                                                              157    189    C5 Resin  Exxon                                     Escorez 1310                                                                              156    186    C5 Resin  Exxon                                     Escorez 1315                                                                              164    204    C5 Resin  Exxon                                     Escorez 1580                                                                              148    179    C5 Resin  Exxon                                     Escorez 2101                                                                              154    185    Aliphatic/                                                                              Exxon                                                               Aromatic                                            Escorez 7105                                                                              163    196    Hydrogenated                                                                            Exxon                                                               C9                                                  Escorez 7312                                                                              163    204    Hydrogenated                                                                            Exxon                                                               C9                                                  Foral AX    148    175    Hyd Wood  Hercules                                                            Rosin Acid                                          Hercotac LA-95                                                                            --     187    C5 Resin  Hercules                                  Hercotac RT-100                                                                           159    186    C5 Resin  Hercules                                  Hercotac RT-1005                                                                          166    192    C5 Resin  Hercules                                  Hercotac RT-115                                                                           169    194    C5 Resin  Hercules                                  Hercotac RT-400                                                                           163    189    C5 Resin  Hercules                                  Nevtac 99   163    189    Polyterpene                                                                             Neville                                                             Resin                                               Permalyn 305                                                                              161    192    PE Rosin Ester                                                                          Hercules                                  Permalyn 85 153    181    PE Rosin Ester                                                                          Hercules                                  Piccofyn A-135                                                                            181    208    Phenolic  Hercules                                                            Polyterpene                                         Piccofyn T-125                                                                            175    203    Phenolic-mod                                                                            Hercules                                                            Terpene                                             Piccolyte A-115                                                                           170    198    Alpha Pinene                                                                            Hercules                                  Piccolyte A-125                                                                           177    203    Alpha Pinene                                                                            Hercules                                  Piccolyte A-135                                                                           183    208    Alpha Pinene                                                                            Hercules                                  Piccolyte C-115                                                                           166    198    d-Limonene                                                                              Hercules                                                            Resin                                               Piccolyte D-115                                                                           171    198    Dipentene Hercules                                                            Resin                                               Piccolyte HM-85                                                                           --     181    Styrenated                                                                              Hercules                                                            Terpene                                             Piccolyte HM-105                                                                          164    192    Pinene Resin                                                                            Hercules                                  Piccolyte S-115                                                                           170    198    Beta Pinene                                                                             Hercules                                  Piccotac 95 157    187    Aliphatic C5                                                                            Hercules                                  Quintone A-100                                                                            158    189    C5 Resin  Nippon-Zeon                               Quintone B-170                                                                            143    173    C5 Resin  Nippon-Zeon                               Quintone C-100                                                                            157    187    C5 Resin  Nippon-Zeon                               Quintone D-100                                                                            159    189    C5 Resin  Nippon-Zeon                               Quintone M-100                                                                            158    187    C5 Resin  Nippon-Zeon                               Quintone N-180                                                                            150    179    C5 Resin  Nippon-Zeon                               Quintone U-185                                                                            153    181    C5 Resin  Nippon-Zeon                               Regalite 355                                                                              159    192    Hyd. Rosin                                                                              Hercules                                                            Ester                                               Regalite 7070                                                                             145    173    Hyd Aromatic                                                                            Hercules                                  Res D-2054  169    197    Styrenated                                                                              Hercules                                                            Terpene                                             Wingtack 115                                                                              171    203    C5 Resin  Goodyear                                  Wingtack 86 161    182    Styrenated C5-                                                                          Goodyear                                                            Terpene                                             Wingtack Plus                                                                             157    204    C5 Resin  Goodyear                                  Wingtack 95 161    187    C5 Resin  Goodyear                                  Zonarez A-100                                                                             164    193    Alpha Pinene                                                                            Arizona                                   Zonarez A-135                                                                             186    209    Alpha Pinene                                                                            Arizona                                   Zonatac 105 167    192    Styrenated                                                                              Arizona                                                             d-Limonene                                          Zonatac 501 167    192    Styrenated                                                                              Arizona                                                             terpene                                             VC Tack 100 --     --     ethylene/ Complex                                                             propylene Chemical                                                            block                                                                         copolymer                                           Adsee 775   --     --     surfactant                                                                              Witco                                                               composition                                         ______________________________________                                    

Diluents

Diluents may be any natural or synthetic material capable of providingthe tackifier component with a kinematic viscosity within the desiredrange specified above. Diluents are preferably light-colored oils (colorless than 4 as determined by American Society of Testing Materials("ASTM") D 1500) such as light-colored naphthenic oils, although otheroils capable of rendering the tackifier a kinematic viscosity varyingfrom about 3,000 to about 5,000 at 100° C. may be used, such as coaloils, rock oils (such as slate oil and the like) and mineral oils (i.e.,hydrocarbons derived from petroleum, such as aromatic, paraffinic andnaphthenic oils). Naphthenic oils are preferred as they do not presentlyrequire hazard labelling during shipping. Preferred naphthenic oils havethe characteristics designated in Table 2.

                  TABLE 2                                                         ______________________________________                                        Preferred Diluent Properties                                                                                    More                                                      ASTM      Preferred Preferred                                   Property      Test No.  Range     Range                                       ______________________________________                                        Viscosity, cST                                                                              D445      55-65     57-63                                       @ 40° C.                                                               Viscosity, cST                                                                              D445      5-10      6-8                                         @ 100° C.                                                              Viscosity Index                                                                             --        40-45     41-43                                       Gravity, API  D287      17-23     18.5-22.0                                   Gravity, Sp., D1250     0.90-0.95 0.93-0.94                                   @ 16° C.                                                               Weight, kg/liter                                                                            D1250     0.95-1.0  0.97-0.99                                   Molecular weight                                                                            D2502     350-450   380-420                                     Flash point, °C.                                                                     D92       >175      185-200                                     Color         D1500     <4.0      <3.0                                        Pour Point, °C.                                                                      D97       >-23      >-25                                        ______________________________________                                    

When the diluent is mixed with the organic resin component to create atackifier, the tackifier will preferably have a T_(g) ranging from about-30° C. to about -50° C.

Organic Oils

Organic oils suitable for reducing dust generation may be any natural orsynthetic oil that is compatible (or capable of being renderedcompatible) with the base granules, the tackifier (both organic materialand diluent), and any adhesion agent used. Typically and preferably theorganic oil is a natural oil selected from the same materials describedpreviously as suitable for the diluent component of the tackifier.Petroleum-derived oils are particularly well suited for use with basegranules such as ceramic-coated slate granules, because they hamper dustformation and provide excellent coating of tackifier and adhesion agenton the granule surface. Of the petroleum-derived oils, paraffinic andnaphthenic oils are preferred over aromatic oils because the former havea more favorable flash point. As previously stated for diluent oils,naphthenic oils are preferred over paraffinic oils for shipping reasons.

When the compositions of the invention are applied to ceramic-coatedslate base granules, which are commonly used as roofing granules, theorganic oil(s) employed should be present in an amount that permits anadequate quantity of granules to be sufficiently coated with a thin filmof the composition of the invention, but not to such an extent that theadhesion of the granules to an asphalt surface of a shingle backingwould be compromised. As the term is used herein, "thin film" means acoating that is less than about 25 micrometers; more preferably lessthan about 20 micrometers. Typically, the thin film would be greaterthan at least 5 micrometers. Preferably, the thin film coating iscontinuous over the base granule surface, but it can be, and usually is,discontinuous. It is preferred that at least 50 percent of the roofinggranule surface be coated with the thin film.

Adhesion Agents

Although the inventive coated granular materials having a dust-reducingcoating comprised of one of the compositions of the invention do notrequire that the coating composition have therein an adhesion agent(such as a silicone oil) to reduce dust generation, compositionsconsisting essentially of tackifier, organic oil, and an adhesion agent,in the proportions used herein, are especially advantageous when thecoated granular material is to be adhered to a surface.

Silicone oils are typically used to promote the adhesion of roofinggranules to asphalt-based substrates and to improve the stain resistanceof the granules, and are therefore the preferred adhesion agents.Silicone oils are essentially chemically inert. Typical and preferredsilicone oils are the organosiloxane silicone oils known under the tradedesignations "Tegosivin" HL15M7 and "Tegosivin" HL100, both availablefrom Goldschmidt Chemical, Hopewell, Va. Other preferred silicone oilsare described in E. Schamberg, Adhesion, v. 29(11), pp. 20, 23-27(1985), as well as in U.S. Pat. Nos. 4,486,476; 4,452,961; 4,537,595;and 4,781,950.

Other adhesion agents that are suitable for use in the invention includethe compositions known under the trade designations "R-20", "R-24","R-27", "R-270", and "R-272" (Union Carbide Corporation, Danbury,Conn.); silicone resins "MK", "M-62" (Wacker-Chemi GMBA, Alemania,Germany); compositions known under the trade designations "Dri-Sil 73","1107" and "477" (Dow Corning Corporation, Midland, Mich.); "SR-82" and"SM 2138" (available from General Electric, Schenectady, N.Y.); andoleic acid, available from Witco Chemical Corporation, Chicago, Ill.Combinations of these adhesion agents may be employed in thecompositions of the invention.

The adhesion agent, when used on ceramic-coated roofing granules, isemployed in the composition of the invention to an extent sufficient topromote granule adhesion to an asphalt-based shingle substrate. Theamount of adhesion agent can vary depending on the composition of theorganic oil, tackifier, and adhesion agent. Generally speaking, adhesionagents are employed at about 0.01 to 2.5 grams per kilogram of substrategranules (5×10⁻⁴ to 0.25 weight percent). In the case where TEGOSIVINsilicone oils are applied to ceramic-coated roofing granules, theadhesion agent is preferably applied to the roofing granules at about0.25 to 0.5 gram per kilogram of base granules (2.5×10⁻¹ to 0.05 weightpercent), more preferably 0.05 to 0.15 gram per kilogram (0.005 to 0.015weight percent).

Base Granules

Although the coatings of the invention have been discussed as beingapplied to roofing granules, as used herein the term "base granules" isused broadly and is intended to include organic and base particleshaving a diameter ranging from about 425 to about 1600 micrometers. Basegranules smaller or larger than this can be used in roofing shinglesprovided they can be adhered to the shingle backing.

Preferred inorganic base granules for use in the invention areconventional and may be selected from any one of a rather wide class ofrelatively porous and weather resistant rock or minerals. Examples ofrelatively porous materials are trap rocks and slates. Examples ofrelatively non-porous rocks or minerals are argillite or greystone (suchas the rock available in the large greystone deposits located north ofWausau, Wis.), greenstone, certain granites, and the like.

When the base granules have a ceramic coating, the preferred ceramiccoatings are derived from the reaction of an aqueous alkali metalsilicate, such as aqueous sodium silicate, and an aluminosilicate.Equivalent materials such as aqueous potassium silicate may also beused. The alkali metal silicate may be designated as M₂ O:SiO₂, where Mrepresents an alkali metal ion such as sodium (Na⁺), potassium (K⁺),mixtures of sodium and potassium ions, and the like. The weight ratio ofM₂ O to SiO₂ preferably ranges from about 1.4:1 to about 3.75:1. Weightratios of 2.75:1 and 3.22:1 are particularly preferred, depending on thecolor of the coated granular material to be produced, the formerpreferred when light colored granules are produced, while the latter ispreferred when dark granules are desired.

The aluminosilicate is preferably a clay having the formula Al₂ Si₂ O₅(OH)₄. Another preferred clay is kaolin, Al₂ O₃ •2SiO₂ •2H₂ O, and itsderivatives formed either by weathering (kaolinite), by moderate heating(dickite), or by hypogene processes (nakrite). The particle size of theclay is not critical to the invention, however, it is preferred that theclay contain not more than about 0.5 percent coarse particles (particlesgreater than about 0.002 mm in diameter). Commercially available anduseful aluminosilicate clays for use in the present invention are thealuminosilicates known under the trade designations "Dover", from W. R.Grace Company, Mcintyre, Ga., and "Sno-brite", from Evans Clay Company,also of Mcintyre, Ga.

The coatable compositions of the invention may be applied to virgin orartificially colored base granules.

When it is desired to prepare artificially colored inorganic basegranules, a precolored base granule may be treated with one of theabove-described inventive compositions to reduce the dust generationfrom the resulting granules during processing and transport of thefinished granules. Preferred precolored inorganic base granules includethose known under the trade designations 3M Brand "5100" Series RoofingGranules, which are black kiln granules; brown kiln granules known underthe trade designation 3M Brand "4100" Series Roofing Granules; and whitekiln granules known under the trade designation 3M Brand "9300" SeriesRoofing Granules, all three available from Minnesota Mining andManufacturing Company, St. Paul, Minn. ("3M").

Either precolored or "virgin" inorganic base granules may be coloredwith various pigments by including a pigment in the ceramic coating.Suitable pigments used in making the coated granular materials of theinvention include red iron oxide, yellow iron oxide, titanium dioxide,chrome hydrate, chrome oxide, chrome green, ultramarine blue,phthalocyanine blue and green, carbon black, metal ferrites, andmixtures thereof.

The data provided in the Examples which follow show results ofside-by-side comparison of base granules treated with a combination ofoil/AlCl₃ with granular materials coated with compositions in accordancewith the invention. The data show that a competent dust-reductiontreatment is provided by the compositions of the present invention,while the amount of oil required is reduced. Typical dust levels forgranules treated with 4 grams slate oil/silicone oil combination (3% byweight silicone oil) per kilogram of base granules (without tackifier)averaged about 300 particles of dust per cubic centimeter of air. Theinventors herein have found that a loading of only about 0.15 gramstackifier, 4 grams oil, and 0.125 grams silicone oil per kilogram ofbase granules controlled dust level to about 30 particles per cubiccentimeter.

The coated granular materials of the present invention typically andpreferably exhibit wet and dry pick test values (as described in theExamples) very close to the values obtained when no tackifier is used.The water repellency of the inventive coated granular materials is alsoexcellent.

The principles of the present invention may be applied to any non-coatedor silicate-based ceramic coated granule, with no limitations as tocolor of the base granules.

Method of Making Ceramic-Coated Base granules Used in the Examples

The method of making ceramic-coated base granules is described in U.S.Pat. No. 2,981,636, col. 5, lines 69-75, bridging col. 6, lines 1-16.

First, a slurry is formed at room temperature (about 25° C.) comprisingan aluminosilicate, such as kaolin, an alkali metal silicate, such assodium silicate solution, and optionally other additives and pigments.This slurry is applied to base granules which are at a temperatureranging from about 150° C. to about 200° C., preferably about 180° C.,in a mixer such as a tumbling-barrel type of mixer.

The granules and slurry are then mixed for several minutes until thegranules are evenly coated with the slurry, and then the slurry-coatedbase granules are dried with warm air until they have a free flowingconsistency.

The coated granules are then fired in a kiln, preferably a rotary kiln,at a temperature ranging from about 300° C. to about 550° C., morepreferably from about 350° C. to about 500° C., for a time sufficient toreact the silicate and aluminosilicate to form "kilned" granules.

The invention will be further described with reference to the followingTest Methods and Examples. In the following Examples, all parts andpercentages are by weight unless otherwise specified.

TEST METHODS Dust Generation Measurement

Granular materials, when processed into roofing granules or other endproducts, may, and generally do have small particles associated withthem (or generated from them) that are not chemically or physicallybonded to the granules. The small particles, which may originate fromeither the coating or the base granules, easily become airborne duringmaterial handling procedures. "Airborne dust", for the purposes of thisinvention, is defined as any particle between 0.5 micrometer and 30micrometers in diameter. This test quantified the dusting for samples ofcoated granular materials.

The testing equipment used to measure airborne dust contained in asample of coated granular material consisted of a dust generationmachine known under the trade designation "APS 3310" AerodynamicParticle Sizer Analysis System and associated hardware and software,available from TSI, Inc., St. Paul, Minn. The system included a diluterknown under the trade designation "APS 3302" which allowed reduction ofthe particle concentration with air. The diluter allowed a dilutionratio of 20:1 to be used, at a total flow rate of 5 standard liters perminute. The diluter operated in a closed system where a small sample of"air" from the sample was diluted with filtered air taken from theoriginal sample. With the closed system, the integrity of the sample wasupheld by maintaining the same temperature, relative humidity, andelemental composition throughout.

The machine was designed specifically to measure concentration ofairborne dust particles using laser refraction. The sample granules andaccompanying dust and dilution air fell through a laminar flow capillarytube (partially by gravity and partially under the influence of theparticle size analyzer) which was placed below the sample inlet.Flowrate was monitored by the pressure drop across the capillary tube.Optical fibers opposed each other across the capillary tube, and whenthe laser beam was broken as the sample fell through, a signal was sent(through a signal processor known under the trade designation "Opto 22",from Optomux Corp.) to an International Business Machines Corporationcomputer known under the trade designation "PS/2 Model 50". The computerreported, using programmed software from TSI., Inc., concentration ofparticles in "particles/cc" of air. The optical fibers, laser, andassociated equipment were available from Banner Engineering Corp.

In running a test, 200 grams of roofing granules to be tested wereweighed and put into the dust generator. The dust generator thenmeasured airborne dust particles for 25 seconds, and reported the totalconcentration of particles ranging in size from 0.5 to 30 micrometers.

In general, for non-white samples prepared or treated in the laboratory,dust levels are preferably below 100 particles/cc. In general, dustingvalues closer than 10 particles/cc, especially when the dusting valuesare under 10, are considered to be essentially the same.

Adhesion Tests (Dry and Wet Pick Tests)

The pick test is a practical test used in the roofing granule industryto predict the adhesive characteristics of roofing granules towardasphalt. Screened granules were dropped into hot asphalt and when theasphalt had cooled to about room temperature, the granules were pickedout of the asphalt. The granule surface which had been in contact withthe asphalt was observed for the amount of asphalt adhering to it. Ifthe surface of the granule was well coated with asphalt, the granule hada good "dry" pick test value. Any reading above 60% coverage of thecontact surface is considered satisfactory.

Effects of water upon adhesion were obtained by submerging theasphalt-granule combination under water for 18 hours. Afterwards,observation of the percent contact surface covered by asphalt wasmeasured. Values above 30% are considered excellent and values above 10%are considered satisfactory.

I. Preparation (Screening) of Granules

Full grade granules were screened through a #14 screen (US mesh, whichpassed particles having size of 1.4 micrometers and smaller) and thosegranules which remained on the screen were used in the Examples and TestMethods.

II. Preparation of Asphalt

A coating asphalt obtained from a typical mid-continent (US) crude oilwas used as purchased from Richards Asphalt Co., Savage, Minn. Theasphalt was heated to 176° C. in a 4.4 liter can with a loose coveruntil the asphalt was fluid. Any skin which formed on the molten asphaltsurface was removed before using. Narrow strips of the fluid asphaltwere poured onto a release paper and cooled to room temperature. Charredasphalt was removed by picking it from the strips of cooled asphalt.

III. Pick Test Procedures

5 grams of prepared asphalt was placed in a can having approximatediameter of about 6 centimeters (cm). The asphalt and can were thenplaced in a dispatch oven at 176° C. for 10 minutes with fullcirculation of air. After 10 minutes the can was removed from the ovenand tapped on a table top once to remove air bubbles. Granules to betested were then sprinkled onto the top surface of the asphalt in thecan from a height of 30.5 cm or more. The can was tapped on a table topthree times to help embed the granules in the asphalt. The can, asphalt,and granules were then left undisturbed and allowed to cool to roomtemperature (approximately 0.5 hour).

The granules were first picked out of the cooled asphalt on a dry basis.Only those granules which were embedded well were examined. A pickedgranule was examined to estimate the amount of asphalt that was adheredto it. The estimate used a scale of 0-100, with "0" meaning no asphaltadhered to the granule and "100" meaning that the part of the granuleembedded in the asphalt was completely covered. Ten granules were pickedout of the asphalt for each of 3 different times (dry, 2 hours, and 18hours) and their total recorded in percent.

For the wet pick test, the procedure was to submerge the granule-coveredasphalt in the same can for two hours under 0.64 cm distilled water atroom temperature. The granules were then re-evaluated. The experiment isrepeated for an additional 16 hours, and the granules furtherre-evaluated.

When performing the pick test it was sometimes noted that the asphalthad a tendency to crack or break around the base of the granule. Whenthis occurred, the test result was ignored. In some cases, especiallywhen performing the wet pick tests, the can was held next to amicroscope light for about 10 seconds (on the lid) and 12-13 seconds (onthe bottom) to slightly warm the asphalt and prevent cracking.

Water Repellency Test

The water repellency is a quality control test frequently used in theroofing granule industry to measure a roofing granule's hydrophobicity.It is important to have hydrophobic roofing granules because hydrophilicgranules exhibit difficulty in being adhered to an asphalt-basedsubstrate. When roofing granules are applied to an asphalt-basedsubstrate, water is sprayed on the asphalt to cool the heated substrate.If the roofing granules are hydrophilic, water can be present betweenthe granules and the substrate, thereby hindering granule adherence tothe asphalt-based substrate.

Water repellency was measured by placing three drops of distilled waterfrom an eye dropper onto a 25 gram pile of roofing granules. The dropswere placed in a depression that had been made in the center of the pileof granules. The three drops of distilled water formed a bead in thedepression. A measurement was taken for the time taken for the bead tobreak up and sink down through the granules. Longer times indicatebetter hydrophobicity.

4-Day Stain Test

The stain test is another quality control test frequently used in theroofing granule industry. The 4-day stain test was an acceleratedmeasurement of the tendency of roofing granules to adsorb asphaltic oilsin an asphalt-based substrate. The granules of each sample were embeddedin asphalt that had been heated to 365° F. (63° C.). The embeddedgranules were placed on a tray in an oven at 176° F. (80° C.) for 96hours (4 days). The trays were removed from the oven, and the asphaltwas allowed to cool to room temperature. The granules were then measuredfor staining under a LabScan colorimeter, and a staining value wascalculated. Stain values range from 0 to 10, with 0 representing nostain (ideal) and 10 representing a dark brown or completely-oiledgranule (which is unacceptable).

MATERIALS DESCRIPTION

The following materials were used in the Examples which follow:

"Tegosivin HL15M7" is an organosiloxane silicone oil, available fromGoldschmidt Chemical, Hopewell, Va.;

"HS-500" is the trade designation for a light-colored naphthenic oilavailable from Cross Oil & Refining Co. Inc., Smackover, Ark.

tackified "HS-500" is the designation used herein for a compositionconsisting of an organic material which is the terpolymer of ethene,1-propene, and 1,4-hexadiene dispersed in "HS-500"; tackified "HS-500"is available from Cross Oil & Refining Co. Inc., Smackover, Ark.;

3M Brand "9300" Series Roofing Granules, white kiln product, availablefrom 3M Industrial Mineral Products Division Pilot Plant, St. Paul,Minn.

Procedure for Treating Granules to Reduce Dust Generation

The procedure used in the following Examples for synthesizing the coatedcoated granular materials of the invention and the Comparative Exampleswas as follows:

1) ceramic-coated white kilned granules prepared as above-described weremeasured into 500 gram samples;

2) each 500 gram sample was heated in an oven in an air atmosphere to182° C. and held at that temperature for at least 2 hours;

3) the heated samples were removed from the oven and immediately placedin a mechanical shaker (one gallon paint can shaker), which was thenturned on;

4) after i minute of shaking, post-treatment oil compositions were addedto sample immediately;

5) the treated granules were allowed to shake for a total of exactly 4minutes; and

6) samples were removed from the shaker, boxed, and allowed to coolovernight.

EXAMPLES Example 1 and Comparative Example A

Granules of Example 1 and Comparative Example A were treated by theProcedure for Treating Granules to Reduce Dust Generation describedabove using white kiln 3M Brand "9300" Series Roofing Granules as thesubstrate granules.

A composition within the invention was first prepared. A tackifier(tackified "HS-500") was first dispersed into slate oil, and then asilicone oil was dispersed into the tackifier/oil dispersion.

White kiln granules then had applied thereto the composition whichresulted in the granules having 4 grams slate oil, 0.15 gram tackifier,and 0.125 gram silicone oil known under the trade designation"Tegosivin" HL15M7 per kilogram of white kiln granules.

The granules of Comparative Example A were coated with a compositionidentical in all respects to that used to coat the granules of Example1, except that the tackifier was omitted.

The coated granules of Example 1 and Comparative Example A were thensubjected to dust generation, dry and wet pick, water repellency, and4-day stain tests. The results of the tests are presented in Table 3.

                  TABLE 3*                                                        ______________________________________                                                       Example 1                                                                              Comp. Ex. A                                           ______________________________________                                        dust count (particles/cc)                                                                      29         310                                               dry pick (%)     72         69                                                wet pick (%)     53         44                                                water repellency (time)                                                                        1 hr +     1 hr +                                            stain (dimensionless)                                                                          5          3.5                                               ______________________________________                                         *Average of six runs                                                     

As can be seen from the data in Table 3, the granules of Example 1coated with the composition of the invention significantly lowered theamount of dust generated, had only slightly lower dry and wet values,similar water repellency value, and a much lower stain value.

Examples 2-11 Affect of Location of Addition of Tackified Oil on DustGeneration

To test the location-dependence of the reduction in dust generated fromceramic-coated base granules, white kiln 3M Brand "9300" Series RoofingGranules were treated with the composition of the invention in aproduction facility. Table 4 lists the location of addition of eachcomposition, and the ingredients in each.

                  TABLE 4                                                         ______________________________________                                                Tackifier Cooler    Belt    Dust                                              Level     Oil.sup.1 Oil.sup.2                                                                             Generation                                Example (wt %)    (gm/kg)   (gm/kg) Value.sup.3                               ______________________________________                                        2       0.2       4         0       56                                        3       0.2       4         2       21                                        4       1.0       2         2       79                                        5       0.2       2         0       274                                       6       1.0       4         2       10                                        7       0.2       2         2       92                                        8       1.0       2         0       279                                       9       0.6       3         1       46                                        10      1.0       4         0       33                                        11      0.6       3         1       37                                        ______________________________________                                         .sup.1 Oil applied at the cooler                                              .sup.2 Oil applied at the belt                                                .sup.3 particles per cubic centimeter                                    

A composition within the invention was first prepared. A tackifier(tackified "HS-500") was dispersed into slate oil to form thecomposition of the invention which was to be applied to the granules. Nosilicone oil was added to the oil in these tests.

White kiln granules exited a rotating kiln at a temperature of about480° C. and fell by gravity onto a chute at an angle of about 45°, whichdirected the granules into a substantially horizontal (angle tohorizontal about 20°) rotating cooler. The cooler was essentially ahollow cylinder having an entrance and an exit for the granules, andwhich had cooling water flowing through an annular space created byinternal and external surfaces. The granules exited the cooler at atemperature of about 110° C.

In Table 4, "oil applied at the cooler" means that oil was applied tothe granules via a pipe extending approximately one fifth the length ofthe cooler and into the cooler granule exit, and along the longitudinalaxis of the cooler. After the granules exited the rotating cooler theyfell by gravity into a chute at an angle of about 60°, which directedthe granules onto a screening device. After the granules exited thescreeninfg device they fell by gravity into a chute into a chute at anangle of about 60°, and then fell onto a conveyer belt which was at anangle to horizontal of about 35°. In Table 4, "oil applied to the belt"means that oil was applied to the granules after they had fallen ontothe second horizontal belt. At this point, the granules had reached atemperature ranging from about 65° C. to about 95° C., depending on thedegree of cooling achieved in the cooler. A typical temperature of thegranules at this point was about 80° C. The granules then dropped off ofthe second moving horizontal belt into a holding tank.

The dust generation values as measured by the method described abovewere generated from samples of granules from each of the runs ofExamples 2-11 (i.e., granules taken from the holding tank after eachrun). As can be seen from the data, the location of addition of thecomposition of the invention significantly affected the dust reductionproperty of the composition. Dust reduction appeared to be optimizedusing the conditions of Examples 4 and 6.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope ofthis invention, and it should be understood that this invention is notto be unduly limited to the illustrated embodiments set forth herein.

What is claimed is:
 1. A coatable composition suitable for reducing dustgeneration during processing of granular materials, the compositionconsisting essentially of:a) an organic oil; b) an optional adhesionagent; and c) a tackifier consisting essentially of an organic materialhaving a glass transition temperature of no less than about 120° C. anda naphthenic oil present in sufficient amount to give the tackifier akinematic viscosity ranging from about 3,000 to about 5,000 centistokesat 100° C.; said organic oil being compatible with the tackifier and theoptional adhesion agent.
 2. Composition in accordance with claim 1wherein the tackifier is present in the composition at about 0.5 toabout 2.0 weight percent of the total weight of the composition, and theadhesion agent is present in the composition at about 0.5 to about 5.0weight percent of the total weight of the composition oil. 3.Composition in accordance with claim 1 wherein the tackifier is presentat about 0.5 to about 1.0 weight percent of the total weight of thecomposition.
 4. Composition in accordance with claim 1 wherein theorganic oil is a mineral oil selected from the group consisting of slateoil, rock oil, coal oil, and seneca oil.
 5. Composition in accordancewith claim 1 wherein the organic oil is slate oil.
 6. Composition inaccordance with claim 1 wherein the organic material has a glasstransition temperature no less than about 150° C.
 7. Composition inaccordance with claim 1 wherein the organic material is selected fromthe group consisting of polyalkylene resins and polycycloalkene resins.8. Composition in accordance with claim 7 wherein the polyalkylene resinis selected from the group consisting of polybutene resins, dipenteneresins, and terpolymers of ethene, 1-propene, and 1,4-hexadiene. 9.Composition in accordance with claim 8 wherein the polyalkylene resin isthe terpolymer of ethene, 1-propene, and 1,4-hexadiene, the diluent is alight-colored naphthenic oil, and the adhesion agent is a silicone oil.10. Composition in accordance with claim 7 wherein the polycycloalkeneresin is selected from the group consisting of phenol-aldehyde resins,terpene resins, rosins, polyethylene rosin esters, phenolic polyterpeneresins, limonene resins, and pinene resins.
 11. A method of reducingdust generation during processing of granular materials, said granularmaterials comprising base granules, the method comprising applying tothe base granules a coatable composition, wherein the coatablecomposition consists essentially of:a) an organic oil; b) an optionaladhesion agent; and c) a tackifier consisting essentially of an organicmaterial having a glass transition temperature of no less than about120° C. and a napthenic oil present in sufficient amount to give thetackifier a kinematic viscosity ranging from about 3,000 to about 5,000centistokes at 100° C.; said organic oil being compatible with the basegranules, the tackifier, and the optional adhesion agent.
 12. Method inaccordance with claim 11 wherein the granular material is heated in akiln to form kiln-fired granular material and subsequently cooled in ameans for cooling to yield cooled granular materials, and thecomposition is applied to the kiln-fired granular material while thekiln-fired granular material passes through the means for cooling. 13.Method in accordance with claim 12 wherein the composition is alsoapplied to the cooled granular material during transport of the cooledgranular material.
 14. Method in accordance with claim 11 wherein saidcomposition includes a silicone oil in an amount ranging from about 0.5to about 5.0 weight percent of the total weight of the coating.
 15. Amethod of making organic oil-coated granular materials comprising thesteps of:a) providing at least one base granule; b) coating the at leastone base granule with a coatable composition in a coating weight rangingfrom about 0.5 to about 10 grams per kilogram of base granules, whereinthe coatable composition consists essentially of:(i) an organic oil;(ii) an optional adhesion agent; and (iii) a tackifier consistingessentially of an organic material having a glass transition temperatureof no less than about 120° C. and a naphthenic oil present in sufficientamount to give the tackifier a kinematic viscosity ranging from about3,000 to about 5,000 centistokes at 100° C.; said organic oil beingcompatible with the base granules, the tackifier, and the optionaladhesion agent.
 16. Method in accordance with claim 15 wherein saidcomposition is devoid of said adhesion agent.